[EU PVSEC] Mitsubishi Claims World's Highest Efficiencies of Polycrystalline Si Solar Cells

Sept 5, 2008 19:44 Motonobu Kawai, Nikkei Microdevices

What excited the visitors to the EU PVSEC were not only oral sessions but also poster presentations. Especially, the one prepared by Mitsubishi Electric Corp attracted much attention.

On the poster, the company presented the results of several researches on its polycrystalline Si solar cells with the world's highest conversion efficiency.

The company's presentation was about two kinds of cells. One is approximately 180μm thick, which is equivalent to the thickness of the existing cells, and has a conversion efficiency of 18.6%. The other cell is 100μm thick and has a 17.4% efficiency.

The values were measured by Japan's National Institute of Advanced Industrial Science and Technology. For 15cm-square polycrystalline Si solar cells, each of them has the world's highest conversion efficiency in its thickness class, the company said.

The development of an anti-reflection film for use on the front surface of the cell and a paste material applied to the back surface by screen printing contributed to increasing the conversion efficiency of the 100μm thick cell to 17.4%, according to Mitsubishi's poster session titled "Improved Efficiency of 17.4% for Ultra-thin mc-Si Solar Cells with Nano-particulate Anti-reflection Coating."

The company formed a MgF2 particulate film on the front surface by using a solution containing MgF2 particles. In addition, the company reportedly added improvements to the paste material on the back surface so that the cell with a thickness of only 100μm will not be bent.

In another poster session titled "Honeycomb Structured Multi-crystalline Silicon Solar Cells with 18.6% Efficiency via Industrially Applicable Laser-process," the company revealed that the key to achieving the 18.6% efficiency was the "honeycomb texture," which reduces the reflectivity on the cell surface.

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